CVE-2026-40854

Description

WNC T-Mobile 5G Box IDU router contains an authentication bypass vulnerability in the portal.cgi component. The session verification mechanism improperly validates the sessionid cookie by checking for the existence of a corresponding file in /tmp/login_user. An attacker can bypass authentication by using directory entries such as "." or ".." in the cookie, allowing unauthorized access to the administration panel.This issue has been fixed in firmware version 1.1.0.651412

Is your site exposed to CVE-2026-40854?

Run a free security scan — no signup, results in seconds.

Weakness Type (CWE)

CWE-290 CWE-290

References

Other References

https://cert.pl/posts/2026/09/CVE-2026-40854

Frequently Asked Questions

What is CVE-2026-40854? +

WNC T-Mobile 5G Box IDU router contains an authentication bypass vulnerability in the portal.cgi component. The session verification mechanism improperly validates the sessionid cookie by checking for the existence of a corresponding file in /tmp/login_user. An attacker can bypass authentication by using directory entries such as "." or ".." in the cookie, allowing unauthorized access to the administration panel.This issue has been fixed in firmware version 1.1.0.651412

How do I check if I'm vulnerable to CVE-2026-40854? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Related Vulnerabilities

CVE-2026-6213

A vulnerability in Remote Spark SparkView before build 1122 allows an attacker to bypasses the local connection check and achieve …

CVE-2026-34025

The Wertheim SafeController Software, AssemblyVersion 6.15.8328.28014, contains an IP restriction bypass vulnerability in the login process. The application restricts user …

CVE-2025-22271

The application or its infrastructure allows for IP address spoofing by providing its own value in the "X-Forwarded-For" header. Thus, …

CVE-2025-31122

scratch-coding-hut.github.io is the website for Coding Hut. In 1.0-beta3 and earlier, the login link can be used to login to …

CVE-2025-46345

Auth0 Account Link Extension is an extension aimed to help link accounts easily. Versions 2.3.4 to 2.6.6 do not verify …

CVE-2025-34053

An authentication bypass vulnerability exists in AVTECH IP camera, DVR, and NVR devices’ streamd web server. The strstr() function is …